The patent relates to a delivery system in which a catheter carries on its distal end portion a stent which is held in place around the catheter prior to and during percutaneous delivery by means of one and preferably two end sleeves which have been coated with a lubricious material. The lubricious material is added to the sleeve material subsequent to extrusion of the sleeve material but prior to a heat curing step. As a result of the heat curing the lubricious material attains a gel or jellied consistency. The stent may be self-expanding, such as a NITINOL shape memory stent, or it may be expandable by means of an expandable portion of the catheter, such as a balloon.
Stents and stent delivery systems are utilized in a number of medical procedures and situations, and as such their structure and function are well known. A stent is a generally cylindrical prosthesis introduced via a catheter into a lumen of a body vessel in a configuration having a generally reduced diameter and then expanded to the diameter of the vessel. In its expanded configuration, the stent supports and reinforces the vessel walls while maintaining the vessel in an open, unobstructed condition.
Both self-expanding and inflation expandable stents are well known and widely available in a variety of designs and configurations. Self-expanding stents must be maintained under a contained sheath or sleeve(s) in order to maintain their reduced diameter configuration during delivery of the stent to its deployment site. Inflation expandable stents are crimped to their reduced diameter about the delivery catheter, then maneuvered to the deployment site and expanded to the vessel diameter by fluid inflation of a balloon positioned between the stent and the delivery catheter. The present invention is particularly concerned with delivery and deployment of inflation expandable stents, although it is generally applicable to self-expanding stents when used with balloon catheters.
An example is the stent described in PCT Application No. 960 3092 A1, published Feb. 8, 1996, the content of which is incorporated herein by reference.
In advancing an inflation expandable stent through a body vessel to the deployment site, there are a number of important considerations. The stent must be able to securely maintain its axial position on the delivery catheter, without translocating proximally or distally, and especially without becoming separated from the catheter. The stent, particularly any potentially sharp or jagged edges of its distal and proximal ends, must be protected to prevent edge dissection and prevent abrasion and/or reduce trauma of the vessel walls.
Inflation expandable stent delivery and deployment systems are known which utilize restraining means that overlie the stent during delivery. U.S. Pat. No. 4,950,227 to Savin et al., relates to an inflation expandable stent delivery system in which a sleeve overlaps the distal or proximal margin (or both) of the stent during delivery. During inflation of the stent at the deployment site, the stent margins are freed of the protective sleeve(s). U.S. Pat. No. 5,403,341 to Solar, relates to a stent delivery and deployment assembly which uses retaining sheaths positioned about opposite ends of the compressed stent. The retaining sheaths of Solar are adapted to tear under pressure as the stent is radially expanded, thus releasing the stent from engagement with the sheaths. U.S. Pat. No. 5,108,416 to Ryan et al., describes a stent introducer system which uses one or two flexible end caps and an annular socket surrounding the balloon to position the stent during introduction to the deployment site. The content of all of these patents is incorporated herein by reference.
This invention provides an improvement over the cited art, by selectively coating or otherwise lubricating the sleeve subsequent to its extrusion yet prior to heat curing. This is in contrast to prior methods of lubricating the sleeve, such as by incorporating a lubricant additive within the polymeric composition of the sleeve, such as described in U.S. patent application Ser. No. 09/273,520, the entire contents of which is hereby incorporated by reference. In addition, the present invention avoids the use of collars, rings or other devices used to secure the sleeves to the catheter by bonding an end of a sleeve to the catheter directly.